This invention relates to diver's control and indication apparatus and, more particularly, to such apparatus which may be worn or carried by a diver for providing certain time and depth calculations and indications relative to an underwater dive.
Growth of the sport of underwater diving, along with the requirements of professional diving, has increased the urgent need for reliable control and indication apparatus for use by a diver. As is well known, a diver is supplied with air at ambient pressure and as the diver submerges the pressure increases such that greater quantities of gases in the supplied air are absorbed by the diver. Of particular concern is nitrogen which, when dissolved in the diver's body under pressure and then allowed to escape rapidly such as by a rapid descrease in pressure during ascent, can lead to severe physiological disorders, referred to generally as the bends or decompression sickness.
Consequently, to minimize these difficulties, limits have been established by various authorities, including the United States Navy, which specify how long a diver may safely remain at a particular depth and then ascend without going through decompression. However, it is also known that if these no-decompression limits are exceeded, the diver can still safely ascend to the surface in slow, controlled decompression stages so as to gradually release excess nitrogen from the body. Thus limits have also been established for decompression stages to be observed as a function of the time and depth of a dive. In addition, diving limits have been established for repetitive dives based upon the duration of previous dives and surface times between dives, the former accounting for previously absorbed nitrogen and the latter accounting for gas released from the diver's body while on the surface.
Heretofore, attempts have been made to provide a diver with various watch-type instruments, depth gauges and the like based generally on one or more of the established limits just mentioned. These attempts have been less than satisfactory since they typically have suffered from one or more disadvantages or shortcomings such as requiring the use of several separate pieces of equipment, requiring difficult underwater manipulations, restricting the diver's freedom of movement, or providing imprecise or difficult to interpret readings.
Further limitations encountered with existing arrangements relate to the quantity and type of diving data that can be handled and indicated to the diver economically.
Accordingly, a need exists for improved diver's control and indication apparatus which will economically and accurately provide various time and depth calculations and indications, and which will provide for greater flexibility and ease of use than known arrangements.